Weight over for alloys of the future
A chance discovery has led to a strong, light alloy that could revolutionise the use of metals in manufacturing
Story Kathy Marks
In 1912, a Sheffield metallurgist named Harry Brearley threw away an uninteresting piece of steel, only to come across it weeks later, shiny and rust-free. And so, as industrial legend has it, stainless steel was born.
A century on, a similar serendipitous discovery has led Monash University scientist Professor Nick Birbilis to develop an ultra-light magnesium alloy that could reduce the weight of cars, trucks and planes by up to 40 per cent, improving fuel efficiency and slashing the greenhouse gases produced by the transport sector, which generates a quarter of global emissions.
Professor Birbilis, who heads Monash University’s Materials Science and Engineering Department, left a piece of magnesium-lithium alloy in a beaker of saltwater and forgot it. Weeks later he noticed that – far from having corroded as he’d have expected – it was pristine. The discovery – a corrosion-resistant magnesium-lithium alloy 30 per cent lighter than already very lightweight magnesium – is possibly the world’s lightest, and strongest for its weight, and offers promise for a wide range of applications.
It is also extremely pliable, says Professor Birbilis, who’s collaborating with Professor Michael Ferry and Dr Wanqiang Xu at the University of New South Wales, and could considerably reduce the weight of products such as laptops and phones, or form armour plating for military vehicles and aircraft.
“It will have prospects in anything that is lifted or requires energy to move.”
Professor Nick Birbilis
“It’s tremendously exciting,” says Professor Birbilis. “It will have prospects in anything that’s lifted or requires energy to move. I expect it to be used to make laptop chassis this year for sure, if it’s not already happening.”
Most magnesium alloys corrode very quickly – some even as fast as aspirin dissolves in water. But this alloy, when immersed in water, releases lithium that reacts with the atmosphere to form a surface layer of rock-like, insoluble carbonate, and re-forms a protective layer when scratched.
It’s also extremely strong relative to its weight, thanks to an atypical atomic structure – the atoms are in a cubic arrangement rather than hexagonal – in addition to forming very unusual, pillar-like nanostructures when heat-treated.
A corrosion expert who likens the job of making alloys to “cooking a lasagna”, Professor Birbilis has devoted his career to creating rust-proof versions of lightweight metals. “We’re working on really exciting stuff, and that’s what drives me,” he says.
The new alloy has created considerable interest in industry and defence circles. Professor Birbilis was invited to deliver a plenary address on magnesium alloys to an aerospace materials conference in Seattle, the home of Boeing, earlier this year. There’s talk of using the alloy in car bodies and wheels.
Consumers, meanwhile, are so hungry for lighter, stronger products that materials engineers are “playing catch-up”, according to Professor Birbilis. “Everyone wants their next phone or laptop to be lighter, and if they drop it, they don’t want it to break. People’s expectations are outstripping what technology can deliver, so the market is driving materials design for the first time.”
Initially partnering with a Chinese aluminium company, Chalco, the team is now using an Australian Research Council Discovery Project grant to investigate how the properties of the magnesium-lithium alloy could be optimised.
That chance discovery in the laboratory has “opened up a box of cool research that we can do in the future”, says Professor Birbilis.